Method and composition for facilitating fitting of dental appliances



United States Patent 3,060,577 METHOD AND COMPGSHTEON FOR FACILITAT- ING FITTING OF DENTAL AP?LIANCES Clark C. Smith, 126 E. Missouri, Kansas City, M0. N0 Drawing. Filed June 12, 1961, Ser. No. 116,292 Claims. (Cl. 32-47) This invention relates to a method and composition for facilitating fitting of dental appliances and particularly to a process for securing dynamic or functional impressions of sound oral tissue within a patients mouth after extraction of his teeth, so that the finished dental appliance for the patients mouth Will fit properly when the denture is in static or functional use.

After extraction of a persons teeth, it has been found extremely difficult to prep-are and fit a dental appliance having an inner surface which accurately conforms to the patients oral tissues when the denture is in functional use. Ill-fitting dentures are a psychological as well as physiological problem because of the pain and soreness which they cause and also because, in many instances, the appliances force the patients tissue to conform to the configuration of the appliance rather than the inner surface of the appliance conforming to normal anatomical tissue form within the patients mouth and under conditions of use of the denture. Thus, impressions are frequently taken by dentists of oral tissue that has been abused by a previous, ill-fitting denture, oral tissue which has for some reason or another been reduced from the normal condition thereof because of having excessive pressure exerted thereon or failure of the denture to fit causing the tissues to be swollen, or gums and tissue that are still suffering from a traumatic condition from whatever cause.

Heretofore, it has been the practice to prepare impressions of a patients gums and surrounding oral tissue by taking a static impression of the patients month. Preparation of a static impression involves inserting a tray in the patients mouth and having impression material thereon so that upon pressing of the material against the persons gums, a suitable impression will be formed in the material. The final appliance is then constructed to con form with the impression made in the setting type of impression material. Little or no efiort is made to obtain an impression while the artificial teeth are actually in use, hence, the term static impression. So-called dynamic impression procedures have been employed heretofore in the art, but these alleged dynamic impressions have been little more than static impressions by virtue of the fact that the impression is still taken over a relatively short period of time and the impression material set or had no life with respect to flow characteristics. Conventional procedure is to have the patient talk for a few minutes, move his jaws or bite down hard on the dental appliance, while an impression is being taken in quick setting material as referred to above.

Thus, a dental appliance made from a static impression will prove satisfactory only to the degree that the impression was satisfactory, if exactly reproduced and if left static and unopposed. The impressions are thereby taken under conditions preventing the tissue from returning to the normal configuration thereof which is especially important where the tissue is swollen or depressed for any reason. In order for the tissue of the patients gums and surrounding areas to return to the normal condition thereof, it is necessary that the tissue not be opposed by a force greater than the patients normal diastolic blood pressure. If the forces against the patients tissues do no exceed his diastolic blood pressure, it can be seen that the swelling of the tissues will be reduced, the tissue which is reduced in size because of excessive prior pressure thereagainst will enlarge and thereby return to its Patented Oct. 30, 1962 normal condition, and eventually the tissue of the patients mouth will assume its proper normal anatomical contour. When the oral tissues have returned to their normal contour, then the dental appliance should be prepared to conform to that contour thereby causing the dentures to properly fit the patients mouth under conditions of use. Until the patients tissues have assumed a normal configuration, fitting of dentures to his gums and surrounding areas will reflect the abnormal condition of the mouth and result in an ill-fitting appliance or require extensive modification and adjustment of the denture in order for the same to be in any sense of the term, comfortable to the wearer.

It is, therefore, the primary object of the present in vention to provide a method of facilitating fitting of dental appliances wherein the patients tissue is restored to a sound physiological condition, a dynamic impression of the sound tissue under actual conditions of use is taken, and a finished denture is constructed which precisely and accurately conforms from a functional standpoint to the gums and surrounding tissues of the patients mouth.

It is a further important object of the invention to provide a method of taking an impression of a patients gums after extraction of his teeth wherein an impressionable composition is placed over the inner surface of a dental appliance and the coated appliance is then placed in the patients mouth and permitted to remain therein for an extended period of time during actual use of the appliance so that the impression in the impressionable composition will accurately conform to the patients oral tissues. In this respect, another significant object of the invention is to provide a method as described wherein the impressionable composition is of a material capable of being defonmed by a pressure not appreciably exceeding the patients diastolic blood pressure, whereby the composition will accurately conform to the patients oral cavity after the appliance has been permitted to remain in the patients mouth for a predetermined extended period.

A still further important object of the invention is to provide a method of fitting dentures wherein the impressionable material is deformable under a pressure not appreciably greater than the patients diastolic blood pressure so that the composition coating the inner surface of the appliance serves as a stimulant and massaging agent providing physiotherapy action to the patients gums and surrounding oral tissue to expedite healing of such tissue and return of the same to the normal healthy configuration thereof.

Another aim of the invention is to provide a novel impressionable composition which has the properties of being deformable under -a pressure of or less than the patients normal diastolic blood pressure, yet is completely nontoxic, has sufiicient viscosity tofirmly hold the appliance in the patients mouth in proper working position, and may be removed from the dental appliance by a simple scraping operation which does not in any way interfere with replacement of the composition. Another important object is to provide an impressionable composition as defined, of a type permitting the dentist to vary the viscosity thereof within certain limits, depending upon the condition of the patients mouth and the necessity of providing a relatively soft impressionable cushion for physiotherapy purposes, or a somewhat firmer coating for tissue in a healthier state.

Other important objectives and details of the present composition and method of employing the same will become obvious or be explained in greater detail as the following specification progresses.

-In accordance with the method of the present invention, it has been found that if oral tissue is opposed with a pressure no greater than approximately a diastolic blood pressure, either hypertrophy, hyperplasia or traumatic conditions can and will correct themselves. This is the basic aim of the process and is accomplished by the patient wearing an appliance having a material thereon of flow characteristics such that the coating will oppose the patients oral tissue with a pressure as near the diastolic blood pressure as possible. The process is conveniently carried out by employing a special treatment material placed over the appliance and changed at predetermined intervals when aging of the composition causes it to harden and lose its required flow characteristics.

In accordance with the dynamic impression method of the present invention, an initial impression is made in a manner very similar to present static impression procedures. From this impression, which is taken with proper consideration being paid to good tissue coverage, centric relation and proper vertical, a therapeutic dental appliance is constructed. It is to be understood that where the patient has had both his upper and lower teeth removed, the upper and lower dentures may be fitted simultaneously in accordance with the present method. In the event the patient is already fitted with a dental appliance which does not fit properly, such old denture may be employed as a therapeutic appliance in the present method but the dentist should ascertain whether any portions of the inner surfaces of the appliance are improperly impinging upon the patients gums or surrounding oral tissues and thus placing excessive pressure thereon. There should be a total lack of excessive impingement of the denture on the patients tissues. If a therapeutic denture is prepared from a static impression described above, such new dental appliance should also be checked to determine that there is not excessive impingement of the appliance on the wearers gums or other supporting tissues.

After the appliance is in proper condition for use, an impressionable composition is prepared and applied to the portions of the inner surface of the appliance normally in contact with the oral tissue of the patients mouth, to thereby provide a coating of generally uniform thickness between the denture and the gums and surrounding areas of the wearers mouth. The impressionable composition is somewhat less viscous when it is applied than it will be a short time later, however, it is of such nature that it will remain pliable for an extended period of time with very slight hardening of the same taking place in 3 to 5 days.

The impressionable composition is preferably a copolymer formed from an admixture of ethyl methacrylate and butyl methacrylate, and employed in conjunction with a plasticizer therefor as well as a quantity of a nontoxic solvent such as ethyl alcohol. In the preferred formulation, 9 parts by volume of ethyl methacrylate to 1 part by volume of butyl methacrylate are copolymerized and the resulting polymer is reduced to powdered form of a particle size whereby all of the material will pass through an 80 mesh screen. The powder is then mixed with predetermined amounts of the plasticizer and a solvent in order to produce a treatment composition of required characteristics. For purposes of explanation only, a suitable composition has been found to be 1 parts by volume of the powdered polymer and 1 part by volume of a liquid including the plasticizer and the solvent. A suitable plasticizer has been found to be butyl phthalyl butyl glycollate with 3 parts by volume of the latter being added to each 1 part by volume of ethyl alcohol.

After stirring of the treatment composition described above, the same is spread over the inner surfaces of the dental appliance with a proper tool and in a manner so that the coating is approximately from 0.1 to 3 millimeters thick. Upon application of the composition to the appliance, the dentist should view the composition and wait until the material ceases to flow readily and stitfens to an observable extent.

The coated dental appliance is then placed in the patients mouth and he is instructed to wear the same for an extended period comprising from 1 day to 3 Weeks but preferably at least 72 hours. In no event should the appliance be permitted to remain in the mouth over a period of time causing the impressional composition to harden to an extent where the material will not be deformed by a pressure not greater than the patients normal diastolic blood pressure or a pressure of about millimeters of mercury.

After the dental appliance has been placed in the patients mouth, he should be instructed to find a comfortable closing position without excessive pressure being placed on the denture. Firm pressure by the patient on the appliance at this juncture in the treatment operation could result in the appliance being forced out of position and necessitating renewal of the treatment composition with an additional layer of the same being required over the appliance. After the patient has gently held his jaws closed for about 3 minutes, in a comfortable position and without excessive pressure on the denture, he should be instrutced to read aloud or talk for a few minutes to effect manipulation of his lips and checks. Any excess material forced from under the denture may be removed at this point and the patient should be instructed to continue talking for approximately 7 to 10 minutes to urge the denture toward a comfortable position and in a normal attitude.

Next, the denture should be removed from the patients mouth and chilled in cold water or the like to temporarily increase the viscosity of the treatment composition whereby excess material may be trimmed away from the borders and margins of the appliance.

The denture should be reinserted in the patients mouth with instructions to return to the dentist if excessive pressure develops for any reason whatsoever. In any event, every 72 hours, even if the appliance feels comfortable in the patients mouth, the impressionable composition should be removed from the appliance and a new quantity thereof applied to the inner surfaces of the denture in a manner as described above. Replacing the treatment composition in this manner promotes a physiotherapy action stimulating the tissues to reduce hyperplasia, hypertrophy and natural healing of traumatic conditions. In this manner a true dynamic impression may be taken of sound healthy tissue that is working in a true harmonious relationship.

In order to permit visual observation of the changes which are taking place in the patients mouth during wearing of the appliance coated with the treatment composition, the dentist should take an impression of the denture supporting tissues of the patients mouth in alginate material just prior to placement of the initial treatment composition on the appliance, and immediately after removal of the appliance from the patients mouth during subsequent treatment periods with the impressionable composition. The alginate impression should be poured with a stone cast thereby providing a diagnostic aid with visual evidence to the dentist of the changes that are occurring in the patients mouth and the improvement to the condition of his gums and surrounding areas. Whenever two successive casts, at least 72 hours apart, appear the same, the patient is thoroughly comfortable with the therapeutic appliance, and the denture has good retention, then a final appliance may be prepared. At the point of satisfactory conclusion of the treatment period, the impressionable composition should be removed from the appliance and replaced in the same manner outlined above. The patient should then use the dental appliance, upon return of the same to his mouth, for several hours or overnight, but not long enough that the treatment composition would be displaced to an extent permitting the appliance to become ill-fitting because of excessive use. The treatment composition on the inner surface of the denture may then be used as an impres sion for preparation of the final dental appliance in accordance with conventional procedures for preparing dentures.

Although a copolymer of butyl methacrylate and ethyl methacrylate has been found to give the best results as a treatment composition for use on the dental appliance, it is to be understood that other equivalent synthetic resins may be employed such as butyl or ethyl methacrylate alone, finely divided styrene, vinyl acetate, cellulose acetate, cellulose nitrate and various other acrylic resins. Under all conditions, the treatment composition, upon application thereof to the appliance, should have a viscosity such that the material will be deformed by a pressure not appreciably greater than 85 millimeters of mercury, but will not be so fluid that the same will be pushed out from under the dental appliance, not conform accurately to the patients mouth, or insuflicient to retain the dental appliance in the patients mouth in proper position and at a proper required attitude. In this respect, the amount of plasticizer should be correlated with the particular resin employed to give the desired results as outlined. Various plasticizers are suitable for the subject purpose provided that the same are compatible with the particular resin and are nontoxic. Diphenyl phthalate may be used with polystyrene in lieu of butyl phthalyl butyl glycollate. Methyl phthalyl ethyl glycollate, ethyl phthalate ethyl glycollate, dibutyl phthalate and a mixture of ortho and para toluene ethyl sulfonamides may all be used with polyvinyl acetate. These same plasticizers may be used with equal results with cellulose acetate and cellulose nitrate.

The length of time required to place the patients mouth in condition for preparation of the finished dental appliance varies considerably from patient to patient, with some treatment operations being concluded in less than one week while other persons may need treatment for up to three months. In any event, the treatment operation should be continued until the patient feels that the appliance is comfortable and stable in his mouth. The finished denture should not be loose but should conform to the patients gums and surrounding tissues in use.

Having thus described the invention what is claimed as new and desired to be secured by Letters Patent is:

l. A method of therapeutically manipulating a patients gums after extraction of his teeth to place the gums in a condition of maximum health permitting taking of a final impression thereof from which a well-fitting, comfortable denture may be prepared, said method comprising the steps of (l) placing a layer of a treatment composition over at least those portions of the inner surface of the base of a therapeutic denture, which normally contact said gums of the patient, said inner surface of the denture substantially conforming to the initial configuration of said gums, said composition being of a consistency capable of being deformed under a pressure not substantially greater than the patients diastolic blood pressure and characterized by the property of retaining such consistency for an extended period of at least about a day;

(2) placing the coated therapeutic denture in the patients mouth in proper functional relationship to opposing teeth in his mouth; and

(3) removing the denture from the patients month only after the patient has used the denture functionally for said extended period of at least about a day and prior to hardening of the treatment composition to an extent that said layer thereof over the therapeutic denture cannot substantially conform to the patients gums.

2. A method as set forth in claim 1 wherein is included the steps of (4) taking an impression of the patients gums after removal of the denture from the patients mouth; and

(5) repeating steps (1) to (4) until two successive impressions of said gums are substantially identical.

3. A method as set forth in claim 1 wherein said composition is a plasticized acrylic resin.

4. A method as set forth in claim 1 wherein said composition is a plasticized copolymer of ethyl methacrylate and butyl methacrylate.

5. A method as set forth in claim 4 wherein the ratio by volume of ethyl methacrylate to butyl methacrylate is approximately 9:1.

6. A method as set forth in claim 1 wherein said composition comprises an admixture of a copolymer of ethyl methacrylate and butyl methacrylate, butyl phthalyl butyl glycollate and ethyl alcohol.

7. A method as set forth in claim 6 wherein suflicient butyl phthalyl butyl glycollate and alcohol are proportioned to cause the coposition to be deformable under a pressure not exceeding about millimeters of mercury.

8. A method as set forth in claim 6 wherein the ratio by volume of ethyl methacrylate to butyl methacrylate is approximately 9:1, and the ratio by volume of the copolymer of ethyl methacrylate and butyl methacrylate to the combination of butyl phthalyl butyl glycollate and ethyl alcohol is approximately 1.5: 1.

9. A method as set forth in claim 8 wherein the ratio by volume of the butyl phthalyl butyl glycollate to alcohol is approximately 3:1.

10. A method of taking an impression of a patients gums after extraction of his teeth comprising the steps of:

(1) placing a layer of a flowable composition over at least those portions of the inner surface of the base of a denture, which normally contact said gums of the patient, said inner surface of the denture substantially conforming to the initial configuration of said gums, said composition being of a consistency capable of being deformed under a pressure not substantially greater than the patients diastolic blood pressure and characterized by the property of retaining such consistency for an extended period of at least about a day;

(2) placing the coated denture in the patients mouth in proper functional relationship to opposing teeth in his mouth; and

(3) removing the denture from the patients mouth after the patient has used the denture functionally for a period of about a day to cause the deformable composition to very closely conform to the configuration of the patients gums during normal functional use thereof, said period being insuflicient to cause the composition to be displaced to an extent permitting the denture to become ill-fitting because of excessive use.

References Cited in the file of this patent UNITED STATES PATENTS 

